1. Field of the Invention
The present invention relates to a brake system for use in a motor vehicle, and more particularly to a brake control system capable of maintaining a braking force even when a brake pedal is released from being stepping-on during a stop.
2. Description of the Related Art
In recent years, in order to lighten the fatigue of a driver resulting from continuous stepping on a brake pedal during waiting for traffic light or running in traffic jam, there has been developed a brake system operating during a stop (which will be referred hereinafter to as an in-stop brake system) which automatically applies the brakes during a stop.
As exemplified by Japanese Unexamined Patent Publication No. 8-48220, there has been known an in-stop brake system designed such that, when a predetermined period of time elapses after a brake pedal is stepped on while a motor vehicle is in stop, an opening and closing valve installed in a brake fluid passage defined between a master cylinder and a wheel cylinder is put in a closed condition to maintain a braking force even if the driver releases the brake pedal from stepping.
There is a problem which arises with such an in-stop brake system, however, in that problems can occur because the driver is required to wait for the predetermined period of time in a state of stepping on the brake pedal until the brake system automatically operates after a stop. In addition, since a braking force is only maintained in accordance with the stepping force by the driver, there is a possibility that the motor vehicle will start to move if the braking force maintained due to the stepping by the driver is low.